An obstacle detection apparatus is known from Patent Publication No. 2007-333609. The known obstacle detection apparatus compares a signal of a received wave of a sonar sensor, which is amplified by a predetermined gain, with a threshold for determining the presence or absence of an obstacle.
In general, a sonar sensor has a shorter sensing distance than a radar sensor which uses an electromagnetic wave (millimeter wave, for example) or a light wave (laser, for example). It is useful to enlarge the sensing distance of the sonar sensor in order to appropriately perform an intervention brake control (or a drive force limitation control) based on object information from the sonar sensor. However, if the sensing distance of the sonar sensor is enlarged, a detection area thereof is enlarged accordingly, which means that a non-target object, which is not a target to be detected and is not detected otherwise, may be detected.